This invention relates generally to road structure processes and apparatus, and more specifically to a new apparatus for extending manhole or vault covers to permit adjustment of the cover to a new height of the road surface cause by resurfacing of the road. The need for extensions or risers for manhole covers is well established because of the many road surfacing jobs which are performed every year. The available extensions, however, generally are of a complex configuration, which increases the cost of manufacture and require, during installation, the removal of the old road surface material all the way around the existing manhole. This procedure leads to a considerable cost of installation and forces the operation to be performed well in advance of the actual resurfacing. Since the manhole risers must be placed before the resurfacing, there is always a considerable period of time during which the risers are protrusions in the old road surface causing much distress to the vehicles using the road. It is, therefore, an object of the present invention to supply a manhole cover riser which is simple and inexpensive to manufacture. It is a further object of this invention to supply a riser for which the installation is simple and not a time consuming operation. A still further object of this invention is to supply a manhole cover rise which has available sufficient adjustment to permit accommodation to various thicknesses of the previously installed manhole cover support.